Superior photocatalytic activity of N-TiO₂/C nanocrystals from the dopant of mucus of oyster than mussel

Heterogeneous photocatalysis employing non-metalloid-doped titanium dioxide (TiO₂) has been extensively investigated for its demonstrated efficacy in pollutant degradation. Among previous studies, biomass dopants by shellfish, as a representative of the utilization of marine biological resources are attracting increasing attention because of their economical, environmentally friendly, and high-efficiency characteristics. However, few studies deeply considered photocatalysis differences in photocatalysis among shellfish mucus as the dopants. We used the mucus of oysters (Crassostrea gigas) and mussels (Mytilus edulis) as carbon and nitrogen sources to synthesize N-TiO₂/C nanocrystals. Three different ratios (2:1, 4:1, and 6:1) were established to investigate the impact of shellfish mucus on photocatalytic performance. The structures of N-TiO₂/C nanocrystals from both shellfish mucus generally varied with different mucus proportions added. The N-TiO₂/C synthesized by oyster mucus showed larger pore volume and smaller pore size, as well as superior photocatalytic performance compared with those by mussel mucus. The maximal photocatalytic efficiency reached 81.39% in 20 min for the degradation of rhodamine B (RhB) in this study, while the ratio of oyster mucus to tetrabutyl titanate (TBT) was 4:1, which might be associated with the lower band gap and fluorescence intensity; and the smaller impedance arc radius in N-TiO₂/C nanocrystals synthesized by oyster mucus. The radical capture experiments indicated that ^•O ₂ ⁻ , ^•OH, and h⁺ were the dominant free radicals to degrade the RhB. This study suggested that the species-specific photocatalytic performance of the shellfish mucus as a source in photocatalytic synthesis.